How do they work? http://www.youtube.com/watch?v=qGAnmRb66s0 Please Register or Log in to view the hidden image!
The video explains it. Note that when the two non-involute gears are meshing they do not transfer torque like normal gears; they transfer it via a tangential force caused by the sloped faces of the respective gears. (In other words, the force does not transfer directly; a torque is transferred to a downwards or upwards force, which is then translated into the opposite torque on the other gear.)
